The present invention relates to a display device, and, more particularly, to a technique which is applicable to gamma correction of a video signal voltage that is applied to respective pixels in a display device.
A liquid crystal display module of a TFT (Thin Film Transistor) type has been used extensively as a display device in a notebook type personal computer or the like.
As an example of a liquid crystal display module, a display module in which thin film transistors (TFT) are mounted on a polysilicon layer (hereinafter referred to as polysilicon type liquid crystal display module) has been known.
Further, as such a liquid crystal display module, there is a display module that employs a method (hereinafter referred to as a PWM method) in which display data within one horizontal scanning line period is stored, and reference data which is sequentially increased or decreased within one horizontal scanning line period is generated; the stored display data and the reference data are compared to each other; and, when these data coincide with each other, a video signal voltage generated by a video signal voltage generating circuit is sampled and is applied to respective pixels (see Japanese Unexamined Patent Publication Hei 6 (1994)-178238 (hereinafter referred to as patent literature 1), Japanese Unexamined Patent Publication Hei 11 (1999)-272242 (hereinafter referred to as patent literature 2)).
As the video signal voltage generated by the above-mentioned video signal voltage generating circuit, a voltage having an inclined voltage waveform (hereinafter referred to as a ramp voltage) is used.